A Review of the Pattern of Malaria in Children above Neonatal Age at the University of Port Harcourt Teaching Hospital (2006-2011)

A retrospective study of children presenting with symptoms suggestive of malaria between 2006 and 2011 was carried out in the University of Port Harcourt Teaching Hospital. Sociodemographic data, clinical information and laboratory investigations were retrieved from the laboratory records of the medical microbiology department. Chi-square analysis was used to assess the prevalence of malaria in the different age groups and sexes. The results showed a 70% prevalence of malaria out of the 23698 patients reviewed. Malaria was significantly higher (χ2 = 18.66, p<0.0001) in male patients compared to female patients There was a significantly higher (χ2 = 6.76, p =0.0093) prevalence (72.70%) of malaria among children under 5 years and 593 (3.47%) patients had severe malaria (≥3+ parasitemia). Severe anaemia, fever and bronchopneumonia were mostly associated with severe malaria. There was an average prevalence of 70.61% from 2006 to 2011. The annual prevalence of malaria declined from 76.7% in 2009 to 60.6% in 2011. The study showed a high prevalence of malaria among the patients, with children under 5 years being the most significantly affected.


Introduction
Malaria is still a major cause of morbidity and mortality globally. [1] In 2010 it accounted for 655,000 deaths all over the world. Nigeria was responsible for 32% of thisdeath s. [1] It is endemic in Nigeria. [1] Malaria has remained a major cause of morbidity and mortality in Nigeria. [1] It has an all year round transmission, Plasmodium falciparum is the predominate specie transmitted by the anopheles mosquitos. [1]There has been a 20% decline in under-five mortality due to malaria from 2010 to 2013. [1] This decline could be attributed to the efforts of the National Malaria Control Strategic Plan (NMCSP) which include amongst others reducing malaria related mortality, reducing malaria parasite prevalence in children under age 5, increasing possession and use of insecticide treated nets (ITNS) and long lasting insecticides nets, introducing and scaling up indoor residual spraying (IRS), increasing the use of diagnostic tests for fever patients, improving efforts related to appropriate and timely treatment of malaria and increasing coverage of intermittent preventive treatment of malaria during pregnancy. [1] According to the current Nigerian demographic and health survey 2013, malaria accounts for 20% under-five mortality. [1] There are about 3.3 billion people at risk for malaria, with about 247 million people affected yearly resulting in a million death mostly in children under the age of 5 years [2]. It accounts for about 50% of the out-patient hospital visits in endemic areas like Nigeria. [3]. Older children may serve as reservoirs for the transmission of malaria, leading to persistent asymptomatic infections [4]. There have been various reports of malaria among school age children, ranging from 11 -26% prevalence especially among children between 8-16 years old malaria endemic countries [5][6][7].
The epidemiological patterns of malaria vary widely in the different regions of Nigeria, with infant malaria posing a major public health challenge. A retrospective review of the prevalence of malaria among children above the neonatal age presenting at the University of Port Harcourt Teaching Hospital, South-South, Nigeria between 2006 and 2011 was carried out in this study.

Study Design
A retrospective analysis of laboratory records of paediatric patients suspected of malaria presenting at the University of Port Harcourt Teaching hospital between 2006 and 2011 was carried out.

Study Area
The study was carried out at the University of Port Harcourt Teaching hospital, a tertiary health care institution located in Port Harcourt, Rivers state, Nigeria. The hospital is a 500 bed capacity hospital which is also a referral center for the Niger-Delta area of Nigeria.

Study Population
The study population consisted of Paediatric patients (1 -192months old) presenting with symptoms suggestive of malaria (fever, malaise, loss of appetite, pain, etc.) to the hospital. Patients between 1 -192 months old were included in the study, while patients less than 1 month old were excluded from the study population.

Data Collection
Data on age, sex, clinical diagnosis, associated conditions, laboratory diagnosis and results of the study population were collected from the data register of the department of medical microbiology of the hospital.

Diagnosis of Malaria
Malaria diagnosis was done by the microscopic examination of Geimsa-stained thin film blood smears from each patient according to standard protocol Ojurongbe et al [5].

Data Analysis
The Epi Info statistical software v7 (CDC, USA) was used to analyze the data collected. The Student's T-test was used to determine the difference in the age groups among patients positive for malaria and those negative for malaria. Chi-square was used to determine the difference in the proportion of occurrence of malaria in the patients according to sex. A p-value of < 0.05 was considered significant and all tests was carried out at a 95% confidence interval.   Table 2 showed a significant difference between patients positive for malaria and patient that did not have malaria (χ 2 : 18.66; p < 0.0001). There were 9619 male patients and 7497 female patients with malaria.  Table 3 shows that 12443 (72.70%) of the patients positive for malaria were below the age of 5 years, 3269 (19.10%) were between 5 -10years old and 1404 (8.20) were between 10 -16 years old. There was a statistically significant occurrence of malaria among the children under 5 years (χ 2 =6.76, p = 0.0093). The occurrence of malaria in the age groups above 5 years old was not statistically significant (p > 0.05) The microscopic grading of parasitemia in the patients showed that 13257 (77.45%) cases of malaria with 1+, 3266 (19.08%) with 2+, while 593 (3.47%) had ≥3+ parasitemia as shown in Table 4.  There was severe complicated malaria in 348 (3.62%) of the male patients and 245 (3.27%) of the female patients, while 9271 (96.38%) of the male patients and 7252 (96.73%) of the female patients had acute non severe malaria (Table 5). The distribution of severe malaria according to age groups showed that severe malaria was significantly high (p <0.0001) among children under 5 years (67.8%), followed by children between 5 -10 years (21.8%) and children between 11 -16 years old (10.5%) as shown in Table 6.  Fig 2 shows that occurrence of malaria ranged from 63.5 % to 65.7% between January and April, while it ranged from 68.1% to 75.0% between May and August. There was a decline in occurrence from 73.5% to 58.0% from September to December.

Discussion
There was a 70% prevalence of malaria among all the patients seen, with 72.7% of the patients with malaria being under the age of five. This is consistent with the 70% transmission rate reported by the WHO in 2015 [8], and prevalence rates between 73 -80% reported in other studies across Nigeria [9][10][11]. This high prevalence may be attributed to the endemic nature of malaria in Nigeria and the large tropical rainforest area of Rivers state. Implications on this high prevalence may include anemia [12], poor cognitive function due to cerebral malaria [13] and increased mortality among school-age children [14].
The occurrence of malaria was significantly higher in children under 5 years old (72.7%). Among the patients with severe malaria, children under the age of 5 years was also significantly affected (67.8%; p < 0.0001). This is similar to the findings of previous studies indicating severe malaria significantly occurs in children below 5 years especially in malaria endemic regions. The Nigerian demographic and Health Survey final report of 2013 also reports that children under age 5 and pregnant women are the groups most vulnerable to illness and death from malaria infection in Nigeria. [1,[10][11][12][13][14][15][16]. Severe anaemia, fever and bronchopneumonia (26.2%, 18.4% and 13.6% respectively) was mostly seen among patients with severe malaria. These conditions have been associated with severe malaria in different studies [6, 13, and 15]. These conditions have also been shown to impair effective immune response to malaria leading to progression of symptoms [16].
The endemic nature of malaria in a country like Nigeria, also translates to continuous exposure to mosquito bites and transmission of malaria parasite that ultimately leads to the formation of high affinity antibodies that inhibit parasite growth and disease progression [1,17].
The study showed that occurrence of malaria peaked during the period of heavy rain (May -July) in the country. This is in agreement with the reports of Olasehinde et al., which reported a peak in the occurrence of malaria during the period of heavy rain fall Nigeria [10]. There is an increase in the pools of stagnant water, leading to an increase in the mosquito population which increases the rate of parasite transmission [18].
There was an average prevalence of 70.61% between 2006 and 2011, with a decline in prevalence of malaria from 76.7% to 60.6% observed from 2009 to 2011. The decline in prevalence may be attributed to efforts by the NMCSP which include amongst others reducing malaria related mortality, reducing malaria parasite prevalence in children under age 5, increasing possession and use of insecticide treated nets (ITNS) and long lasting insecticides nets, introducing and scaling up indoor residual spraying (IRS), increasing the use of diagnostic tests for fever patients, improving efforts related to appropriate and timely treatment of malaria and increasing coverage of intermittent preventive treatment of malaria during pregnancy.( intermittent preventive treatment using sulphadoxine-pyramethamine (IPT-SP) treatment for malaria control in Africa) [1,18,19].

Conclusions
Malaria was significantly more prevalent in children under 5 years. Though there was a decline in prevalence